The present invention relates generally to an improved plug-in cartridge adapter in a phonograph pick-up. More particularly, the invention relates to a cartridge adapter which enables a plug-in cartridge for a linear tracking arm to be mounted on an offset arm such that a minimum of manual operations are required to change cartridges and tone arm imbalance is not introduced in the change of cartridge.
Recently, there has been extensive use in the phonographic arts of a linear tracking arm which is designed so that a tone arm is moved both linearly and radially with respect to a recording disc (see, for example, U.S. Pat. No. 3,572,724). The advantage of a linear tracking arm is that no inside force is generated since the cantilever of the cartridge is always directed perpendicular to the modulated groove of the recording disc. Normally, a plug-in type cartridge is used for the linear tracking arm wherein the cartridge is directly inserted into a female connector mounted at the tip of the tone arm. The linear tracking arm and cartridge are designed to be compact, and the terminal pins are smaller in diameter than those of prior art cartridges. By way of comparison the cartridge for an offset arm generally has mounting holes which are spaced about one-half inch apart, and the cartridge is fixed by two screws to the head shell which is coupled to the tone arm. The linear tracking plug-in cartridge is not however provided with mounting means for the conventional offset arm head shell, and the diameter of each of the output terminal pins is too small for the female connectors on conventional offset arm head shells. Hence, the linear tracking plug-in cartridge is incompatible with conventional offset tone arms.